Since a fluorophosphate glass has low dispersibility and abnormal partial dispersibility, it is a glass effective for a high-level correction of chromatic aberration, it is frequently used as a material for a lens that is positioned most closely to the side of a photographic subject, which is called a front lens, in a telephoto lens, or the like. A fluorophosphate glass has a problem that it shows significant volatility and corrosive property in the production steps thereof, and the present inventors have disclosed inventions for solving the above-mentioned problem in Patent Documents 1 and 2, by adjusting the molar ratio (O2−/P5+) of the amount of O2− and the amount of P5+ in a glass to 3.5 or more.
Furthermore, a fluorophosphate glass has the following problem even after the production of the glass. A lens made of a fluorophosphate glass is made, for example, by grinding and polishing a glass that has been processed into a lens shape; however, during the polishing, a deteriorated layer called grinding burn is easily formed on the surface of the glass. This is a problem attributed to the chemical durability of the fluorophosphate glass.